Deuteronomy 24:8
Take heed in the plague of leprosy, that thou observe diligently, and do according to all that the priests the Levites shall teach you: as I commanded them, so ye shall observe to do. Take heed in the plague of leprosy, that thou observe diligently, and do according to all that the priests the Levites shall teach you: as I commanded them, so ye shall observe to do.
Deuteronomy 24:8 falls within the section of Deuteronomy that reviews the law for Israel's new generation. Within that review it belongs to the repetition in chapters 23, 24 and 25 of various laws regarding duties between man and man, and between man and God.
Moses commanded and wrote the law contained in Deuteronomy 24. Jesus taught that Moses was the human author of the Pentateuch, and His appeal to what Moses commanded and wrote in Deuteronomy 24 proves that Moses wrote this law.
Apart from offering sacrifices, it was the business of the priests the Levites to teach the people the way of the Lord. The people receiving that true instruction were held responsible to observe and do it, to perform what they had been taught.